My 2007 Mercedes GL450 (131k miles) got a CEL. OBD2 scanner says:
1208-Constant adjustment of intake camshaft of right cylinder bank in direction 'Retarded' (P0016)
1200-Constant adjustment of exhaust camshaft of right cylinder bank in direction 'Retarded' (P0017)
If erased, the codes would come back at the next engine startup.
Engine starts and runs smooth with no rattle noise or other unusual noise.
I replaced all four magnets and all four sensors on both banks, and cleaned up engine oil leaked into the electric connector of wire harness. did not help,

It rides great with four new Michelin defender 2 ($1400 last year), and new front struts.
Other recent fixes within last 3 years:
Front control arms upper & lower, both sides replaced 2 year ago
New brake rotor and pads
steering fluid reservoir, steering pump replaced 1 year ago

Called several local European car repair shops,
half of them would directly tell me that this is a well known well documented issue for 2007 M273 engine, it's the balancing sprocket gear that is worn. And repairment will cost about $6000-7000 (labor rate $197/hr).
Took it to one of the shops that did not directly quoted me, They checked and said the timing is off. Their estimate is $1600 if replacing timing chain, guide and tensioner. but they are not sure if the sprocket will need to be replaced.

Been keeping up with all maintenance and repairment on the GL450, It's the most comfortable car I've ever had. But the sprocket replacement is probably beyond my DIY ability, and $6000 is probably not worth it for this 19 year old GL450. Maybe it's finally time to let go. I do have lots of new GL parts that I've bought that will be available for sale.

Thanks a lot,

The way I look at it, for 6000 dollars, can you buy anything out there as nice as what you currently have? I plan on fixing mine as long as I can. Cheaper than starting over again with a new vehicle.

besides that 6k price sounds more like “I don’t want the job” price. I have done timing chain tensioners on three different Audis, about $350 in parts and a few nights and some wrenches.

Thanks for the encouragement. I actually enjoy working on the M273 engine, lots of space and easy to work on. It's a Lego set for me and I enjoy the process.
I've DIY replaced all the following:
power steering reservoir, power steering pump
Radiator, idler pulleys, tensioner, belt, thermostat, radiator hoses
front struts with airbag, rear air bags, air compressor, manifold, front speed sensors, Brake pads
12v main battery and auxiliary battery, cleaning/repair front SAM, various bulbs
Reseal engine oil cooler & engine oil filter housing
Engine oil & filer, air filters, cabin air filters

Mobile mechanic replaced the starter for me.

Brand new OEM parts I bought and haven't installed:
Intake manifold
water pump
Mercedes transmission fluid

All these DIY work was done using bits & pieces of time I squeezed out of my daily work and kids activities. Sometimes the GL would need to sit in the driveway for couple of days till the repair work is done.
The wife is fed up with that because it takes time away from kids duty, and put more pressure on her side. That's the main reason to let go the GL.

Then you should have zero issues fixing the tensioners if you’ve already did all that work already, as I said, not hard. Just a lot of stuff to remove (on the Audi at least)

yes, just a lot of work

FYI, we have a couiple 2014 GL450's available locally for sub $8000. 114k & 146k mileage respectively. NO WAY on EARTH would I invest $6k in repairs on a 2007 GL when I could get an almost decade newer version for a couple thousand more. And heaps more all the way up to 2016 available under $12k. Sadly, after 10 years of age GL's values drop like a rock. Luckily, as you know, they still have at least another decade of life left in them, so there is plenty of value out there available.

2014 GL450 $7995

2014 GL450 $7500

In that case, its a no brainer. I would do it. Unfortunately these don't come up for sale too often (diesels) in my area.

wow they look great. They have turbo engines after 2012. Only question is if those turbo engines reliable and easy to work on like old M273.

you’re trading one issue for another. Early X166s have rampant bore scoring issues.

As far as this 2007 goes, it is a known issue and it is finally manifested itself in yours. Your idler gear is worn and you are out of time and eventually the engine will grenade itself.

A cost effective way to fix this is just to swap the engine for a 2008 or newer production M273 with a serial number greater than 066811. And then you get the choice of having the 5.5 or 4.7 L version!

options:
1. Blow six grand on this cars engine and add another grand for while you’re in there.
2. Just replace the whole engine with a newer lower mileage 4.7 L or 5.5 L M2 73.
3. Sideline this one for parts and buy a newer X164 for about the same ($6k).
4. Sell with known issues for around thousand to 1500 bucks as parts car.

yes another option is to trade in to dealer when buying a new car.. end of DIY repair activities for couple of years.

I'm kind of puzzled. If this is a known common issue, why I'm not seeing lots of discussion on this in this forum.

I agree, I don't hear much about it on this forum, but on the other hand, pretty much EVERY engine has this issue at some point in its life. I think it comes down to basic maintenance. If you do regular maintenance most engines will last a very long time. Neglect them and stuff like this happens over time. It's just basic mechanical wear.

checking my record:
from 2007 to 2016 (till 73k miles): oil change once a year at MB dealership,
from 2017 to 2019 (100k miles), four oil changes, so every 7k miles
After that till now 131k mils: 8 oil changes, about every 4k miles

But this 2007 GL450 was actually made around Sep of 2006, maybe the first batch of GL450.

That's more than enough oil changes, actually too often, but that's just money. lol

most of these issues manifested fairly early in life for these cars, which would’ve been about a decade ago.

no, they only had a certain run of engines with the bad idler gear in it. Engine numbers less than 088611 can be affected. That equates to somewhere in 2007 production. For 2008 through 2012 GL this issue did not present itself other than as you stay with poor oil, change intervals, etc. etc. but then you would have a whole host of other issues along with that.

If you google M2 73 idler gear issues there are numerous older posts about these failing and other M2 72 and M2 73 powered Mercedes.

nothing wrong with your oil change intervals you just had a cam chain idler gear that wasn’t properly heat treated before it got put into the motor.

here’s a pretty good YouTube video explaining what is going on with your motor:

Thanks for the information. looked up my GL450 on website: www.LastVIN.com
for sure my M273 engine number is far less than 088611, delivery date 6/24/2006
The related BalanceShaftTSB attached.

For what it's worth, I had a very early build 2007 GL450 (built 06/2006) withn the same issue/codes, at about the same mileage. When the "easy" potential fixes didn't work, I just drove it like it was - FOR ANOTHER 100,000 miles! I was not willing to dump a bunch of money in it when was worth so little. Ran great the entire time. Finally sold it to someone else for $4k with 238k miles on it. I know it was still running past 260,000 miles... So, If the CEL doesn't drive you crazy, just drive it.

I went with 3 but went W instead of X when mine was having timing issues and also needed tires and a windshield since I no longer needed the third row. It just wasn't worth fixing when prices are so low on replacements with fewer miles and problems.

That's really good to know. I wasn't worried about the CEL until I found out that it can not pass annual state inspection with the CEL.....

It's listed for sale now:
https://mbworld.org/forums/market/923023

Good luck with your sale! I wouldn't recommend a 2013-2014 X166 with the M278 as a replacement. I had a 2013 GL450, and it had a lot of issues with the cooling system and electronics. That M278 turbo engine had power when the turbos kicked in but it ran HOT, I could feel the heat in the garage when I came home from a long drive or towing. The electric fans often ran at high speed to keep the engine cool and were noisy. Eventually it had bore scoring issues and I had to sell it for cheap. I actually went BACK to the X164 platform and bought a 2010 GL450 as a replacement last year (same color and miles as my 2013, just without the turbo engine). My 2010 is a little slower than the 2013, but it can still tow the same and is the same size and drives very similar. The tech is older, I miss the 360 view camera, but I'm happy with the 2010 so far and plan on keeping it a long time. If you replace your X164 with an X166, go with 2015 or newer.

Thanks a lot for the info. I got a Tesla Model Y juniper with FSD, don't want to drive anymore

Tesla???!

ummm, ok then.